1. Field of the Invention
The present invention relates to a radiator which is used for a motor vehicle or the like and is equipped with a tank containing an oil cooler for cooling oil of an automatic transmission or others.
2. Description of the Related Art
A conventional radiator equipped with a tank containing an oil cooler is disclosed in Japanese patents laying-open publication No. 2005-315514, No. 2005-337529, No. 2005-308303, No. 2005-172270 and No. 2005-3227. In these conventional radiators, parts of the radiators including the oil cooler and the tank are brazed to each other by heat treatment at the same time, in a state where the oil cooler is contained in the tank and two connecting pipes of the oil cooler pass through a wall portion of the tank to be fixed. Incidentally, in other cases, the oil cooler and the tank are brazed to each other before the heat treatment of other parts of the radiators.
These conventional radiators, however, encounter a problem in that an undesirable deformation of the tank are liable to occur due to a thermal expansion difference caused during the heat treatment, especially in an intermediate portion, sandwiched between a pair of connecting pipes of the oil cooler, of the tank.
FIGS. 10A and 10B show how the tank is deformed after the heat treatment.
In order to easily insert the oil cooler 05, with the connecting pipes P01 and P02 projecting outwardly therefrom, into the tank 03, the tank 03 is usually divided into a first tank body 03A fixed with and a second tank body 03A.
The first tank body 03A is formed with a pair of through-holes for passing the connecting pipes P01 and P02, and the second tank body 03B is formed so as to be coupled with the first tank body 03B. This needs brazing of the connecting pipes P01 and P02 and a wall of the first tank body 03A and another brazing of the first tank body 03A and the second tank body 03B. It is preferable to carry out the both brazing at the same time, because its production time and manufacturing costs can be decreased by removing twice-heating, twice taking in-and-out and cooling the first tank body 03A and the oil cooler 05 after they are brazed.
As shown in FIG. 10A, the oil cooler 05 is temporally assembled with the first tank body 03A in a state where its connecting pipes P01 and P02 penetrate through a wall portion of the first tank body 03A to be fixed. Then the first tank body 03 is temporally coupled with the second tank body 03B. The tank 03 containing the oil cooler 05 is temporally assembled with a core part and others, and then they are placed in a heating furnace to be heated.
In this heat treatment of the radiator, heating temperature and heating hours are usually set, allowing for appropriate ones for mainly those of brazing the core part, the first tank body 03A and the second tank body 03B. Wall portions of the first and second tank bodies 03A and 03B are exposed to an ambient atmosphere in the heating furnace and are directly heated, while the oil cooler 05 is kept out of the direct heat of the heating furnace because the wall portions of the first and second tank bodies 03A and 03B prevent the oil cooler 05 from being directly heated. The temperature of the wall portions rises more rapidly than that of the oil cooler 05, which causes the wall portions to expand with heat, more largely than the oil cooler 05. Accordingly, an intermediate portion 03a, sandwiched between the connecting pipes P01 and P02 which penetrate the wall portion of the first tank body 03A, of the wall portion of the first tank body 03A deforms outwardly due to a thermal expansion difference between the first tank body 03A and the oil cooler 05 with the connecting pipes P01 and P02 as shown FIG. 8B. The wall portion is liable to easily deform because of a division into the first and second tank bodies 03A and 03B. The outward deformation of the first tank body 03A may cause a leakage of coolant flowing through the tank 03, deteriorating product quality and reliability of the radiator.
The above-described problem similarly occurs when the oil cooler 05 and the tank 03 are brazed in advance of the heat treatment of the other parts.
It is, therefore, an object of the present invention to provide a radiator containing an oil cooler which overcomes the foregoing drawbacks and can prevent a wall portion, through which connecting pipes of an oil cooler penetrate, of a tank from being deformed beyond permissible limit when the tank body and the oil cooler contained therein are brazed by a heat treatment, improving product quality and reliability of a radiator.